Simon is the person Diane seems to have chosen for her lover at this time in her life and yet Jason thinks Simon is the least possible good for Diane. What do you think Jason means by this?

Jason prefers to attack the problem of Spin head-on and try to find solutions to its existence or at the very least to learn more about Spin. Diane, on the other hand, has chosen to hide her head in the sand through religion, an act of which Jason greatly disapproves. So the reason Jason thinks Simon is not what Diane needs is because it is Simon who brings Diane into the religious cult and who convinces her that it is the only place she is "safe."